MXPA06011791A - Packaging articles, such as opaque bottles, and production method thereof. - Google Patents

Abstract

The invention relates to opaque packaging articles, such as bottles, which can be used to store certain products, such as milk, such that they are shielded from visible and UV radiation. More specifically, the invention relates to: an opaque bottle which is obtained by means of injection blow moulding using a polyester-based composition, and a method of producing said packaging articles, particularly bottles. The polyester composition comprises a mineral filler containing a white pigment such as titanium oxide or zinc sulphur.

Description

it allows it to be conserved during relatively short or relatively long periods. In this way, sterilized fresh milk should be used very soon after it is bottled, while UHT (ultra high temperature) milk can be stored for several months after it is bottled. This very long storage time imposes restrictions on the storage container, such as bottle or cardboard. This is because the taste of the milk changes through the effect of visible and / or UV radiation. A milk that has its flavor deteriorated by this effect is called as having a "taste affected by light". This change is especially due to the degradation of vitamin B2 (riboflavin) in milk as a result of being exposed to light. The degradation of this vitamin in milk varies according to the intensity of the light source, the time of exposure and also the wavelength range of the light source. The radiation with a wavelength between 350 and 520 nm seems to be responsible for the degradation of this vitamin and therefore the deterioration in the taste of the milk. Accordingly, the storage or packaging containers for these containers must have a very low or no transmission of light for radiation with wavelengths of less than 550 nm, and more generally for UV radiation, and visible radiation. This specification is increasingly important as the milk storage time is extended. This restriction is very important for long-lived milks, such as UHT milk (with ultra-high temperature treatment), and also for certain types of vitamin milk that is sensitive to radiation and for dairy products such as yogurt, cream or similar. Solutions for the production of containers compatible with the prolonged storage time of milk have already been proposed and widely used. One of the most used containers is a cardboard box made of multilayer cardboard to ensure low light transmission for the visible and UV wavelength range. However, the closing systems of these cardboard boxes, especially after the first use, are not practical and do not guarantee effective closure. To remedy the disadvantages of these cardboard boxes, such as stiffness, dead space, shape, size and workability, it has been proposed to use bottles, especially bottles made of high density polyethylene (HDPE).

However, to obtain a low level of light transmission, these bottles are formed by multilayer walls which may comprise three to six layers produced in different ways. The outer layers generally contain a white pigment, consisting of titanium oxide, in order to give an attractive appearance compatible with the stored product. As an intermediate layer, there is a layer with low light transmission. This layer generally includes a carbon black as a light absorbing filler. Finally, an oxygen barrier layer may also be present, and also adhesive layers in order to give the structure good stability. These bottles require complex manufacturing processes. Additionally, its recovery and recycling capacity are difficult to implement due to the presence of several different materials.

Description of the invention The object of the invention is in particular to remedy these disadvantages by proposing a new process for the preparation of containers or articles, especially packaging articles, which have a very low light transmission especially in the wavelength range between 350 and 550 nm, and more generally for UV radiation and visible radiation. These items can be made by simple processes, already used for the preparation of conventional containers, and can also have the advantage of being able to be easily recycled for the same use, as they are obtained from an individual material and when recycled they do not degrade the intrinsic properties of the material. For this purpose the invention proposes a process for manufacturing articles, especially for packaging products such as foodstuffs, by forming a composition comprising a polyester or polylactone thermoplastic product and at least one opacifying filler consisting of a bulking agent. mineral filler, white chosen from the group consisting of titanium oxides and zinc sulphide, with a concentration by weight of between 2 and 40%, preferably between 4 and 20%, based on the total weight of the composition. The term "packaging articles" is understood to mean flexible films obtained by extrusion, cardboard boxes or containers obtained by injection molding, and more particularly hollow bodies such as bottles obtained by injection molding and blow molding. According to the invention, the articles are formed by a single layer obtained from a composition as defined above. According to a preferred feature of the invention, the articles obtained according to the process of the invention have a light transmission factor of less than 0.25% for wavelengths between 350 and 550 nm, especially between 400 and 550 nm, and more preferably less than 0.1% in this wavelength range. The term "light transmission factor" is understood to mean the ratio of the light intensity of the radiation emanating from the wall to the light intensity of the incident radiation applied to the wall. The measurement of these intensities is carried out on the radiation in a direction perpendicular to the surface of the wall. In this way, the transmission measured in the present invention is called "normal transmission" or "normal transmission factor". This transmission factor depends on the nature of the filling agent, the concentration of the filling agent and the wall thickness of the article. In this way, the articles obtained by the process of the invention have a normal transmission factor of less than 0.25% for wall thicknesses between 0.2 and 0.6 nm. Advantageously, the normal transmission factor is less than 0.20% and preferably less than 0.1%.

According to the invention, the mineral filler is a white pigment, such as titanium oxides in the rutile and / or anatase form. These titanium oxides are in the form of particles of various sizes, advantageously between 0.2 μt ?? and 1 μt ?. These particles may be pure titanium oxide particles or may comprise a titanium oxide core with a protective coating. This protective coating, which can be formed by one or more layers of oxides of various metals and / or organic compounds, makes it possible to reduce or even eliminate by interaction between the titanium oxide and the polymer forming the matrix of the composition. This is because the fillers suitable for the invention must exhibit properties and characteristics that eliminate or avoid any action that may deteriorate the process for making the polyester or its properties. According to the invention, another mineral filler that forms a white pigment, especially zinc sulphide, allows suitable compositions to be obtained for the manufacture of articles, especially packaging articles that exhibit adequate light opacification for a concentration of agents. filling compatible with the processes to form the composition and its manufacture. According to another characteristic of the invention, the processes for forming the composition according to the invention are conventionally used processes for the formation of polyesters and the production of articles of various shapes and sizes. The articles obtained according to the process of the invention may be films, molded parts, extruded profiles or hollow bodies made by the use of conventional processes, such as injection molding, extrusion, stretch extrusion or injection and blow molding. The injection and blow molding processes used for the production of polyester bottles used especially for storing water or carbonated beverages are suitable for the production of bottles of a composition according to the invention, which contains a mineral filler. The adjustments for the injection and blowing conditions are normal for those skilled in the art and the like for those necessary to adopt the process of injection molding and blowing to a conventional polyester. The articles, especially bottles, obtained are formed by a single layer of material and have a suitable attractive appearance, especially for storing milk or milk products. The properties of very low light transmission of the walls of the bottle allow this bottle to be used to store milk or milk products for a very long period of several months, without seeing any deterioration in the taste of the milk. Accordingly, this bottle is suitable for bottling long-lived milk or light-sensitive milk such as UHT milk, vitamin milk or other light-sensitive products. Furthermore, by using a plastic such as a polyester or polylactone, it is possible to obtain packaged articles, especially bottles, which exhibit good mechanical properties and can be easily recycled. In general, the articles obtained according to the process of the invention, that is to say with a polyester or polylactone composition containing a mineral filler chosen from titanium oxides or zinc sulphide, are particularly suitable for the storage of sensitive products. to the light. Additionally, these items exhibit better aging resistance as the mineral filler, reflecting most of the light rays and absorbing UV rays, protecting the polyester, especially in the core of the wall and on the unexposed surface, of the effect of light radiation. This effect is particularly important in the case of thick articles such as, for example, extruded profiles. According to the invention, the term "polyester" is understood to mean a polyester resin chosen from polyethylene terephthalate, polyethylene naphthalate, polyethylene terephthalate copolymers and polyethylene naphthalate copolymers, which may contain at least one compound that retards crystallization or repeat units. Later in the present, the term "polyethylene terephthalate or PET" will be used. However, the characteristics, processes or uses described with respect to this polymer also apply to polyethylene naphthalate. In a preferred embodiment of the invention, the polyester resin is obtained from ethylene glycol and terephthalic acid or its asters. These resins are often denoted by the acronym PET. The term "PET or polyester resin" denotes both a homopolymer, obtained solely from terephthalic acid monomers or their esters, such as dimethyl terephthalate and ethylene glycol, and copolymers comprising at least 92.5% by number of repeating units of ethylene terephthalate. These polymers are the preferred polymers of the invention. The polyester may also include at least one crystallization retarder which makes it possible, especially during the cooling of the molded or injection molded article, such as a pre-form, to slow or retard the recrystallization of the polyester to crystallize it in this way as very small, preventing spherulitic crystallization, and to allow the development of an article with acceptable mechanical properties. These properties may be beneficial in certain applications. These crystallization retarders are difunctional compounds, such as diacids and / or diols, which are added to the monomer mixture before or during the polymerization of the polyester. As crystallization retarder, mention may be made by way of example of: diacids, isophthalic acid, naphthalene dicarboxylic acid, cyclohexanedicarboxylic acid, cyclohexanediacetic acid, succinic acid, glutaric acid, atypical acid, azelaic acid, and sebacic acid; and as examples of diols, mention may be made of aliphatic diols comprising from 3 to 20 carbon atoms, cycloaliphatic diols having from 6 to 20 carbon atoms, aromatic diols comprising from 6 to 14 carbon atoms and mixtures of the same, such as diethylene glycol, triethylene glycol, isomers of 1,4-cyclohexanedimethanol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, (2, 4) -3-methylpentanediol, (1,4), 2-methylpentanediol, (1, 3) 2, 2, 4-trimethylpentanediol, (1,3) -2-ethylhexanediol, (1,3) -2, 2-diethylpropanediol, 1,3-hexanediol, 1,4-di (hydroxyethoxy) -benzene, 2,2-bis (4-hydroxycyclohexyl) ropano, 2, -dihydroxy-1,1,3,3-tetramethylcyclobutane, 2,2-bis (3-hydroxyethoxyphenyl) propane, 2, 2-bis (4-hydroxypropoxy-phenyl) propane and mixtures thereof. Diethylene glycol is frequently inherently present in polyesters as it is formed during synthesis by the condensation of two ethylene glycol molecules. Depending on the desired concentration of the repeating units comprising a residue of diethylene glycol (DEG) in the final polyester, either the diethylene glycol is added to the monomer mixtures or the conditions of polyester synthesis are controlled in order to limit the formation of diethylene glycol. Advantageously, the molar concentration of diethylene glycol in the polyester in relation to the number of moles of diacid monomers is less than 3.5% mol, preferably less than 2% mol. The polyester resins used for the invention have a viscosity index VI that can be within a very wide range, advantageously between 0.5 dl / g and 1.2 dl / g, preferably between 0.6 dl / g and 1 dl / g. The viscosity index VI is measured in a polymer solution containing 0.5 g of polymer in 100 ml of a solvent consisting of orthodichlorobenzene / phenol (50/50 by weight) at 25 ° C, according to ISO 1628 / 5 of 06/15/1986. The polymer solution is obtained by taking the weight of the filler into account, in order to obtain a concentration of 0.5 g of polymer, minus the filler. The viscosity index is generally determined by analyzing the polymer granules obtained at the end of polymer processing. When the thermoplastic compositions of the invention are used to produce hollow bodies or bottles, this viscosity index VI can be measured in the polymer constituting the walls of a bottle. To carry out this measurement, a portion of the bottle is cut and then cut into small pieces to allow them to dissolve. In general, the viscosity index of the polyester is severely affected during the process of making the hollow body. However, the viscosity index measured on the wall of the bottle can be less than or greater than that measured in the feed granules in the injection molding step. The value measured in the granules is generally close to that determined in the bottle. These considerations are also applicable with respect to the viscosity index measured in the polyester formed by the walls of the preform obtained after the injection molding step. The thermoplastic composition of the invention may contain other components, such as dyes, brighteners, heat and light stabilizers, antioxidants and acetaldehyde traps, by way of example. This list is given only as an indication and is not exhaustive. According to the invention, the composition is made using conventional processes for making polyester. In a preferred embodiment, the mineral filler or white pigment is added at the beginning of the polymerization, in the mixture containing the monomers, as will be described later. The process of the invention can also be carried out by using as the starting material, a composition obtained by recycling articles, for example elaborated bottles of a similar composition. In this way, the collected bottles are milled into particles. These particles can be treated, for example washing and granulating, before they are fed in a process for producing bottles by injection molding and blow molding according to the invention. The process for making the thermoplastic compositions of the invention comprises a first step of esterification or transesterification in the presence or absence of a catalyst. The hydrolyzate or esterified product obtained is then polycondensed under reduced pressure in the presence of catalysts, such as, for example, antimony, titanium or germanium compounds. In this step, alcohol or water is removed in order to allow the polycondensation reaction to progress. According to the invention, this polycondensation is stopped when the degree of polycondensation or the viscosity index has reached the desired value. The obtained polyester is flowed through nozzles to have rods which are then converted into granules by cutting. These granules can be subjected to thermal treatment, either to increase the viscosity of the polymer (a solid state post-condensation heat treatment or SSP) or to reduce the acetaldehyde content (drying and evaporation at a temperature below that of an SSP treatment). According to another embodiment of the invention, in order to limit the degree of polycondensation during the thermal treatment described above in order to decrease the acetaldehyde content, the polyester may include a monofunctional monomer, preferably a monoacid. The molar content of the monofunctional monomer is between 0.5 and 3 mol% relative to the total content of the diacid monomers.

The monoacids suitable for the invention are, for example, benzoic acid, naphthalene acid, aliphatic acids having a boiling point compatible with the polyester synthesis process, that is to say advantageously at least above that of ethylene glycol or their esters or monoalcohols such as cyclohexanol or aliphatic alcohols, which also advantageously have a boiling point above that of ethylene glycol. For example, various additives, such as brighteners, dyes or other additives, light or heat stabilizers or antioxidants, can be added to the polyesters of the invention either in the polymerization step or in the molten polymer before injection molding. . According to a preferred embodiment, the mineral filler or white pigment is advantageously suspended in a monomer of the polyester to be processed. As the preferred monomer for producing this suspension, mention may be made of the diols used in the manufacture of the polyester, such as ethylene glycol. In addition, the dispersion of the mineral filler in the composition is better when the dispersion in the monomer before the addition is homogeneous and when the filler is dispersed in the form of very small particles that do not contain coarse agglomerates. These dispersions can be produced with any known means, such as conventional mechanical stirrers, ultrasonic devices and high power mixing devices, such as Ultra-Tur axle homogenizers. The white pigment suspension is advantageously added to the reaction mixture in the esterification or transesterification step. The concentration of white pigment in the ethylene glycol is such that the amount of ethylene glycol used for this step can represent between 20 and 100% of the total ethylene glycol needed to synthesize the polymer. Additives can be used to make this suspension easier to make. However, the pigment can be added directly to the reaction mixture, in the various steps of polymerization, esterification and polycondensation, in the powder form, without departing from the scope of the invention in this way. The pigment can also be incorporated, in the form of powder or a main batch or concentrated solutions, into the polymer after it has been synthesized, directly before the granulation of the polymer, or by mixing it with the polyester granules before they are melted. In order to feed the formation process, such as the processes of injection molding or extrusion. This pigment can also be added directly to the molten polymer before it is fed in the previous formation process. The use of a masterbatch with a high concentration of mineral fillers, for example more than 30% by weight, is one of the preferred methods for implementing the invention. The main batch advantageously comprises a polymer matrix, also made of polyester. It is obtained in the form of granules and can be made using the polymerization process described above, or the mineral filler powder is added to the polyester melt. Advantageously, the granules of the main batch are mixed with the polyester granules before introduction into the forming devices, especially the means for melting the composition, or they can be dosed into the flow of polyester granules at the entrance of the training devices. The granules of the main batch can also be added directly to the polyester melt. One of the particular important uses of these compositions, and it is this one that forms the subject of the present invention, in the manufacture of hollow bodies such as bottles with the technique of injection and blow molding or articles obtained by injection molding. In these uses, the thermoplastic composition according to the invention is produced in the form of granules of various sizes, or is formed in situ in the feeding and melting devices of the formation medium, based on a polyester resin that does not contain mineral fillers, with addition, either in the solid state or by feeding into the already melted resin , of the mineral filler in the form of powder or main batch, as described above. The granules of the composition, polyester resin and / or main batch, are advantageously dried in order to obtain a moisture content of less than 50 ppm, preferably less than 20 ppm. This drying step is necessary without the moisture content of polyester is sufficiently low. In some cases, it may be advantageous to dry only the polyester and introduce the main batch without drying. Then, the granules are introduced into an injection and blow molding process to make hollow containers such as bottles. These processes, described in numerous publications and used on a wide scale in the industry, comprise a first step of injection molding in order to manufacture pre-forms. In a second step, the preforms, which may or may not be cooled, are reheated so that they are blow molded into the shape of the desired bottles, optionally by biaxial stretching. The preforms are obtained, for example, by melting the resin in an individual screw or twin screw injection molding press, which also allows the polyester to be plasticized and fed under pressure into a dispenser provided with heated nozzles and plugs, for example, heated to a temperature between 260 ° C and 285 ° C. The composition is injected into at least one mold for the preform, then cooled in order to obtain a solid preform. The mold is provided with a suitable cooling medium in order to control the cooling rate of the preform and thus avoid spherulitic crystallization, which can be a problem in the blow molding step. Rapid cooling is also necessary in order to obtain short times of the injection molding cycle and therefore high production speeds. After the pre-form has solidified, it is ejected and either cooled to room temperature, so that it is subsequently stored and blow-molded, or maintained at an intermediate temperature and introduced directly without further cooling, into an installation of blow molding as described below. In this preform manufacturing process, the polyester is melted at a temperature of about 280 ° C, for example between 270 and 285 ° C, and then injected into molds. Advantageously, the lowest possible injection temperature will be used in order to limit the formation of acetaldehyde, especially to reduce the rate of acetaldehyde formation. Additionally, it is advantageous that the molds are cooled to a temperature between 0 ° C and 10 ° C. This cooling is obtained by using any suitable refrigerant, such as, for example, water with glycol. Advantageously, the time of the injection / cooling molding cycle is between about 10 seconds and 1 minute. The polyester forming the wall of the preform obtained using this process has a viscosity index of between 0.45 dl / g and 1.2 dl / g, advantageously between 0.60 dl / g and 1 dl / g. The preforms obtained in this way are generally used in blow molding processes to manufacture bottles. These blow molding processes are also widely used and are described in numerous publications. They generally consist in introducing the preform into a blow molding installation that includes a heating means, with or without excessive stretching. The preform is heated to at least above the Tg (vitreous transition temperature) of the polymer and then pre-blow molded by injecting a pressurized gas at a first pressure during a first period. A second injection of a gas at a second pressure allows the final shape of the bottle to be obtained before its injection molding, after cooling Advantageously, the pre-form heating temperature is between 80 ° C and 105 ° C. This heating is carried out by any suitable means, for example by infrared radiation directed on the outer surface of the preform. This heating is advantageously controlled to avoid obtaining too great a temperature difference between the inside and the outside of the preform. Advantageously, the pre-blowing of the preform takes place at a first pressure of between 4 x 105 Pa and 10 x 105 Pa (4 bar and 10 bar) for a time between 0.15 and 0.6 seconds. The second blowing is carried out at a second pressure of between 3 x 106 Pa and 4 x 106 Pa (30 and 40 bar) for a second time of between 0.3 and 2 seconds. A stretching rod can also be introduced, in a known manner, into the preform during the pre-blowing and / or blowing operations in order to partially stretch the preform. The bottles obtained in this way are produced with walls formed by a single layer of material. They have an attractive white appearance compatible with the storage of food products such as milk. Other colors can be obtained by combining with the fillers of the invention the colored pigments that can be added to the polymerization mixture or mixed in the PET granules before they are melted for injection molding. As illustrated above, they can be obtained using conventional processes for manufacturing hollow bodies by injection molding and blow molding. In addition, these bottles can have mechanical properties that allow them to be used in hot filling processes and processes that include a step of sterilization or pasteurization. These mechanical properties are also suitable for storing the bottles in a stacked manner, either the ambient storage temperature. The bottles obtained in this way have very low normal light transmission. In this way, after the UHT milk was stored for 3 months, the taste of the milk did not deteriorate as judged by a panel of tasters. The invention also makes it possible to produce bottles of different volumes in various ways, as is already the case for translucent polyester bottles which is used to store food products, such as water. Other advantages and details of the invention will become apparent in view of the examples given below by way of illustration but not implying limitation.

Example 1 The synthesis was carried out in a batch installation consisting of two successive stainless steel reactors, each with a volume of 200 liters. The first reactor, equipped with a screw / shaft agitation system and with a column that allows the glycol and the formed water to separate, was used to carry out the esterification step under pressure. The second reactor, equipped with a screw / shaft agitation system, was used to carry out the polycondensation step, under a gradual vacuum. In this example, the mineral filler used was rutile titanium oxide sold under reference 2220 by Kronos. The concentration by weight in the composition obtained was 4%. The synthesized polyethylene terephthalate contained 2.3 mol% of isophthalic units, ie the acid monomers used were a mixture of terephthalic acid (TPA) and isophthalic acid (IPA), the mixture containing 2.3 mol% of IPA. The ratio of the number of moles of ethylene glycol (EG) to the total number of moles of diacids is 1.20. The catalyst used for the polycondensation was antimony oxide and its concentration by weight, expressed in Sb, was 250 ppm with respect to the weight of the polymer theoretically obtained from the mass of the monomers included.

Raw materials used: - terephthalic acid (TPA) 103,796 kg (624.99 moles) - Isophthalic acid (IPA): 2,444 kg (14.71 moles) - ethylene glycol (EG): 47,616 kg (768 moles) - Rutile Ti02 (2220 of): 5.340 kg - Sb203: 36.8 g Preparation of the mineral filling agent: 35 kg of glycol (part of the 47,616 kg indicated above) was introduced, at room temperature, into a stainless steel vessel and then, with vigorous stirring, 5.340 kg of titanium oxide was added gradually, for example ultrasonic agitation. Agitation was maintained for 15 minutes after the end of the introduction of Ti02. The glycolic suspension of titanium oxide was transferred to the esterification reactor containing the rest of the glycol (12,616 kg). The terephthalic acid / isophthalic acid mixture was added with stirring. After purging the reactor with nitrogen and then pressurizing it under an absolute nitrogen pressure of 6.6 bar, the temperature of the reaction mass was gradually increased from 25 to 260 ° C for 60 minutes, from 260 to 270 ° C for 10 minutes Y. finally from 270 ° C to 285 ° C for 40 minutes. The esterification reaction was initiated when the temperature of the reaction mass reached about 240 ° C. The degree of reflux of distilled water was adjusted so that the temperature at the top of the column remained at 167-168 ° C throughout this step of esterification. When the water distillation was finished, the pressure in the reactor was brought back to atmospheric pressure. Then the antimony oxide was introduced into the reaction mass. This mass was transferred to the second polycondensation reactor, which has been inerted beforehand with nitrogen and heated to 280 ° C. The pressure in the reactor was progressively decreased to 1 mbar, with stirring. At the same time, the temperature of the reaction mass was increased to 285 ° C. The pressure was then maintained between approximately 1 and 0.5 mbar. The polycondensation was monitored by measuring the torque of the agitation. The speed of this agitation was gradually reduced as the viscosity of the reaction mass increased. The total duration of the polycondensation under a pressure of less than 1 mbar was 190 minutes. At the end of the polycondensation, the agitation torque reached 81.6 mN. The obtained polymer was extruded through a nozzle in order to produce a rod that was cut into granules.

Example 2 Example 1 was repeated, but twice the mass of rutile Ti02 2220 in order to obtain a concentration by weight of 8% in concentration. The total duration of the polycondensation under a pressure of less than 1 mbar was 180 minutes. At the end of the polycondensation, the agitation torque reached 83.8 mN. The obtained polymer was granulated under the conditions indicated in Example 1.

Example 3 Example 1 was repeated, but with rutile Ti02 replaced with anatase type Ti02 sold by Sac tleben under the trademark HOMBITAN LO CR S M, with the same weight content of 4%. The synthesis conditions were identical to those of the previous examples. The total duration of the polycondensation under a pressure of less than 1 mbar was 175 minutes. At the end of the polycondensation, the agitation torque reached 92.5 m. The obtained polymer was granulated as in Example 1.

Example 4 Example 3 was repeated, but with twice the mass of Ti02 of HOMBITAN LO CR S M of Sachtleben in order to obtain a concentration of Ti02 of 8% by weight in the composition. The synthesis conditions were identical to those of the previous examples. The total duration of the polycondensation under a pressure of less than 1 mbar was 140 minutes. At the end of the polycondensation, the agitation torque reached 97 mN. The polymer obtained was granulated as in Example 1. The characteristics of the polymers obtained are given in Table I: Table I The coloration was determined by measurement using a MINOLTA CR310 colorimeter according to the CIE L * a * b * standard. Before conversion, the polymer granules crystallized, being stored under vacuum for 16 h at 130 ° C. To verify the level of opacification of the various synthesized polymers, films were produced by hot pressing of the granules, the thickness of the films obtained and characterized to be of the same order of magnitude as that of the wall of the injection molded bottles. / blow molded in general. The results of residual UV / visible transmission obtained are given in Table II: Table II (*) wavelength (?) below which no residual transmission can be detected, that is, less than 0.01%.

The UV / visible residual transmission values of the films obtained were measured in a Perkin Elmer Lambda 9 spectrophotometer. These tests clearly show the very low or even zero level of normal transmission of the films obtained with the compositions of the invention. These results are representative of those obtained with the walls of a bottle produced with a composition according to the previous examples. In addition, the bottles of 0.5 liters of volume reproduced with the compositions of Examples 2 and 4. These bottles were filled with milk according to the UHT method and kept for 3 months under an illumination of 300 lux representative of lighting in warehouses . The stored milk was approved according to the conventional procedure for flavor evaluation. The milk had a non-deteriorated flavor, that is, a "taste unaffected by lux".

Example 5 The synthesis of the composition according to the invention was carried out in a stainless steel batch reactor of 7.5 liters volume. This reactor is equipped with: - a double-helix ribbon agitation system equipped with a torque meter that allows the polycondensation step to be monitored, by evaluating the viscosity of the reaction mass; - a column for separating the water from the glycol, during the esterification step. This reactor operated under pressure during the esterification step, and under reduced pressure during the polycondensation step. The mineral filler used was HOMBITAN LC-S anatase titanium oxide sold by Sachtleben. The concentration by weight of titanium oxide in the composition obtained was 8 ¾. number of isophthalic units and the molar ratio of ethylene glycol / total number of moles diacids were the same as in the case of Examples 1 to 4, as was the amount of antimony oxide used.

Raw materials used: - terephthalic acid (TPA): 2595 g (15,632 mol) - isophthalic acid (IPA): 61.1 g (0.368 mol) - ethylene glycol (EG): 1190 g (19.2 mol) - Ti02 anatase (HOMBITAN LC-2) ): 268 g - Sb203: 0.938 g A suspension of the filling agent was prepared by introducing, in a laboratory beaker of 2 00 g of glycol, at room temperature, and stirring in 268 g of Ti02 in a homogenizer of the Ultra-Turrax type. The mixing was maintained with stirring for 3 minutes. The glycol slurry of Ti02 was then introduced into the esterification reactor together with the rest of the ethylene glycol. After purging the reactor with nitrogen, the nitrogen pressure was increased to 6.6 bar absolute. The temperature was increased from 25 to 260 ° C for 50 minutes, maintained at 260 ° C for 30 minutes and finally gradually increased to 280 ° C, for 50 minutes. The esterification reaction started when the temperature of the reaction mass reached approximately 250 ° C. The degree of reflux in the column was adjusted to have a temperature at the top of the column of 161-162 ° C. After the distillation of the water originating from the esterification was completed, the pressure in the reactor was brought back to atmospheric pressure. Then the antimony oxide, dissolved in advance at 160 ° C in 30 ml of glycol, was introduced hot into the reaction mixture. The pressure in the reactor was decreased progressively to 0.7 mbar, for 80 minutes. At the same time, the temperature was increased to 285 ° C, for 50 minutes, and then maintained at this temperature. The polycondensation was monitored by measuring the agitation torque, and stopped when this torque reached 2.3 IÍ. The polycondensation time was 60 minutes. The polymer obtained was then granulated once extruded in the form of a rod in a water bath and the edge cut into a granulator.

Example 6 Example 5 was repeated, but with anatase-type titanium oxide HOMBITAN LC-S replaced with anatase-type titanium oxide 1075 sold by rones, with the same content of 8% by weight in the final composition. The synthesis conditions were identical to those of Example 5. The polycondensation time was 53 minutes. The polymer was granulated under the same conditions as in Example 5.

Example 7 Example 5 was repeated, but with the anatase-type titanium oxide HOMBITAN LC-S replaced with anatase-type titanium oxide 1014 sold by Kronos, with the same content of 8% by weight. The synthesis conditions were identical to those of examples 5 and 6. The polycondensation time was 72 minutes. The polymer was granulated under the same conditions as in Example 5.

Example 8 Example 5 was repeated, but with anatase-type titanium oxide HOMBITAN LC-S replaced with titanium oxide anatase type A-HRF sold by Huntsman, with the same content of 8% by weight. The synthesis conditions were identical to those of examples 5 to 7. The polycondensation time was 80 minutes. The polymer was granulated under the same conditions as in Example 5.

Example 9 Example 5 was repeated, but with anatase-type titanium oxide HOMBITAN LC-S replaced with anatase-type titanium oxide A-PP2 sold by Huntsman, with the same content of 8% by weight. The synthesis conditions were identical to those of Examples 5 to 8. The polycondensation time was 55 minutes. The polymer was granulated under the same conditions as in Example 5. The characteristics of the polymers obtained are given in Table III: Table III (*) This concentration was determined by measuring the ash content, by pyrolysis of the composition at 800-850 ° C. The results obtained from the normal residual UV / visible transmission, determined using the method described for examples 1 to 4, are given in Table IV: Table IV EXAMPLE 10 This example describes the production of pre-forms and bottles, using a composition according to the invention obtained by mixing a main batch based on PET, containing 60% anatase-type titanium oxide HOMBITAN LO-CR-SM (from Sac tleben), with a PET polymer containing 2.1 mol% of isophthalic units, the viscosity index of the composition which is 83 ml / g. The mixing weight ratio was 13.3% from the main lot to 86.7% polyester. The granules of the main batch and the granules of the polyester resin were mixed uniformly beforehand. The preforms were manufactured using a HUSKY LX 160T injection molding machine, comprising a double-impression mold with a 42 mm diameter screw. The obtained pre-forms have a neck of 28 mm and the cycle time was 14.4 seconds. The conditions of injection molding were as follows: - temperature profile of the melting zones in the barrel containing the screw: 270 ° C - 275 ° C -275 ° C - 275 ° C - 275 ° C - 275 ° C - 275 ° C - 275 ° C -275 ° C - 275 ° C; - screw speed: 44% of the maximum speed allowed by the machine; - Temperature profile of the injection molding cylinder: 270 ° C - 270 ° C - 270 ° C; - injection time: 2.45 seconds; - injection pressure: 34 bar; - cooling water temperature: inlet: 4.2 ° C outlet: 4.8 ° C. The preforms obtained with a composition containing 8% by weight of Ti02 have a weight of 27.7 g. The preforms were blow molded in a SIDEL SBO 1 injection molding press equipped with a 500 ml bottle mold and two ovens equipped with successive infrared lamps in order to heat the preform according to the defined heating profile. In the tests below, the first oven was not used and the lamp settings of the second oven are indicated in Table V below. The blow molding conditions used are indicated in the Table V: Table V Speed (bottles / h) 1000 Lamp power (second 10 0 oven) (%) 9 0 8 0 7 0 6 S4 5 60 4 50 3 40 2 29 1 30 Surface temperature of the pre-forms 101 ° C pressure Pressed 9 bar Blowing 35 bar duration Presoplado 0.12 s Blowing 1.45 s Degassing 0.50 s Total time of the 2.07 cycle s The thickness of the body of the obtained bottles was approximately 350 μp ?. The values of normal transmission of residual UV / isible for the obtained bottles were the following: - wall thickness: 345 μp? - Cut-off threshold: 440 nm - residual normal transmission? = 400 nm: < 0.01%? = 500 nm: 0.015%? = 600 nm: 0.03%? = 700 nm: 0.045%

Claims (1)

1. CLAIMS 1. Process for making articles, especially for packaging or storing materials, characterized in that it consists of forming a composition comprising a polyester matrix and at least one mineral filler that constitutes a white pigment selected from the group comprising titanium oxide and zinc sulfide, the mineral filler that is present at a concentration by weight of between 2% and 40% relative to the total weight of the composition. Process according to claim 1, characterized in that the titanium oxide is selected from titanium oxide in the form of rutile and / or titanium oxide in the anatase form. Process according to claim 2, characterized in that the titanium oxide is in the form of particles coated with one or more protective layers. Process according to one of the preceding claims, characterized in that the polyester is a polyethylene terephthalate or polyethylene naphthalate comprising at least 92.5% by number of repeating units of ethylene terephthalate or ethylene naphthalate. Process according to one of the preceding claims, characterized in that the composition is obtained by molding a polyester resin with a main batch comprising at least 30% by weight of mineral filler which constitutes the white pigment. Process according to claim 5, characterized in that the main batch comprises a polyester resin as a matrix. Process according to any of the preceding claims, characterized in that the packaging articles are in the form of film, molded parts, extruded profiles or hollow bodies obtained by injection molding, extrusion molding, extrusion molding by stretching or molding. injection with blowing. Process according to claim 7, characterized in that the hollow bodies are bottles obtained by injection molding and blow molding. Packaging articles obtained by the process according to one of the preceding claims and having a normal light transmission, the wavelength range that is between 350 and 550 nm, of less than 0.25% and preferably less than 0.1 % for a wall thickness between 0.2 mm and 0.6 mm. 10. Article according to claim 9, characterized in that the article is a bottle obtained by injection molding and blowing, the wall of the body of the bottle having a normal transmission of light of less than 0. 25% 11. Use of the articles according to claim 9 or 10 for storing milk or milk products. The invention relates to opaque packaging articles, such as bottles, which can be used to store certain products, such as milk, such that they are protected from UV and visible radiation. More specifically, the invention relates to: an opaque bottle which is obtained by means of blow molding and injection using a polyester-based composition, and a method for producing the packaging articles, particularly bottles. The polyester composition comprises a mineral filler that contains a white pigment such as titanium oxide or zinc sulfide.